June 2001 - Haskell - Haskell.org

tuple component functions
by trb＠eastpac.com.au 03 Jan '03

03 Jan '03

S.D.Mechveliani writes: > As Haskell has the standard functions fst, snd to decompose (a,b), > maybe, it worths to provide also > tuple31, tuple31, tuple31, > ... > tuple51, tuple52, tuple53, tuple54, tuple55 > > for the tuples of n = 3,4,5 ? I've found some of these useful, except I named them differently: > fst3 :: (a,b,c) -> a > fst3 (x,_,_) = x > snd3 :: (a,b,c) -> b > snd3 (_,x,_) = x > thd3 :: (a,b,c) -> c > thd3 (_,_,x) = x .... never got around to quadruples etc. I also defined (some of these may be untested): > tripl :: a -> (a,a,a) > tripl x = (x,x,x) > curry3 :: ((a, b, c) -> d) -> a -> b -> c -> d > curry3 f x y z = f (x, y, z) > uncurry3 :: (a -> b -> c -> d) -> ((a, b, c) -> d) > uncurry3 f t = f (fst3 t) (snd3 t) (thd3 t) > applyTriple :: (a -> b, a -> c, a -> d) -> a -> (b,c,d) > applyTriple (f,g,h) x = (f x, g x, h x) > cross3 :: (a -> b, c -> d, e -> f) -> (a,c,e) -> (b,d,f) > cross3 (f,g,h) (x,y,z) = (f x, g y, h z) > mapTriple :: (a -> b) -> (a, a, a) -> (b, b, b) > mapTriple = cross3 . tripl > applyFst3 :: (a -> b) -> (a, c, d) -> (b, c, d) > applyFst3 f = applyTriple (f . fst3, snd3, thd3) > applySnd3 :: (a -> b) -> (c, a, d) -> (c, b, d) > applySnd3 f = applyTriple (fst3, f . snd3, thd3) > applyThd3 :: (a -> b) -> (c, d, a) -> (c, d, b) > applyThd3 f = applyTriple (fst3, snd3, f . thd3) > applyArgs3 :: (a -> b) -> (c -> d) -> (e -> f) -> (b -> d -> f -> g) -> (a -> c -> e -> g) > applyArgs3 af1 af2 af3 f = \x y z -> f (af1 x) (af2 y) (af3 z) > rotl :: (a -> b -> c -> d) -> (b -> c -> a -> d) > rotl f y z x = f x y z > rotr :: (a -> b -> c -> d) -> (c -> a -> b -> d) > rotr f z x y = f x y z > rotl4 :: (a -> b -> c -> d -> e) -> (b -> c -> d -> a -> e) > rotl4 f y z t x = f x y z t > rotr4 :: (a -> b -> c -> d -> e) -> (d -> a -> b -> c -> e) > rotr4 f t x y z = f x y z t Some more combinators (only for pairs so far): > twin :: a -> (a,a) > twin x = (x,x) > swap :: (a,b) -> (b,a) > swap (x,y) = (y,x) -- apply a pair of functions to one argument > applyPair :: (a -> b, a -> c) -> a -> (b, c) > applyPair (f, g) x = (f x, g x) -- apply a pair of functions to a pair > cross :: (a -> b, c -> d) -> (a, c) -> (b, d) > cross (f, g) = applyPair (f . fst, g . snd) -- compose a pair of functions onto one function > dotPair :: (a -> b, a -> c) -> (d -> a) -> (d -> b, d -> c) > dotPair (f, g) h = (f . h, g . h) -- compose a pair of functions onto a pair of functions > dotCross :: (a -> b, c -> d) -> (e -> a, f -> c) -> (e -> b, f -> d) > dotCross (f, g) (h, i) = (f . h, g . i) > mapPair :: (a -> b) -> (a, a) -> (b, b) > mapPair = cross . twin > applyFst :: (a -> b) -> (a, c) -> (b, c) > applyFst f = applyPair (f . fst, snd) > applySnd :: (a -> b) -> (c, a) -> (c, b) > applySnd f = applyPair (fst, f . snd) > applyArgs :: (a -> b) -> (c -> d) -> (b -> d -> e) -> (a -> c -> e) > applyArgs af1 af2 f = \x y -> f (af1 x) (af2 y) > betweenFst :: (a -> b -> c) -> (a, d) -> (b, e) -> c > betweenFst = applyArgs fst fst > betweenSnd :: (a -> b -> c) -> (d, a) -> (e, b) -> c > betweenSnd = applyArgs snd snd I find these combinators useful, and probably other people have their own versions - it would be nice to get them standardised, so we all speak the same language. By standardised, I mean a prominent version that will be adopted by users, not necessarily a committee process. Tim

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ICFP programming contest
by trb＠eastpac.com.au 03 Jan '03

03 Jan '03

Michael Hobbs writes: > Just took a look at the results for the ICFP contest. Am I correct in > assuming that "LA" stands for Lennart Augustsson and that "Si^3" stands > for Simon Marlow, Simon Peyton-Jones, Sigbjorn Finne? Is there a URL for the results ? Tim

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CFP: JFP on SAIG
by Walid Taha 08 Jul '01

08 Jul '01

CALL FOR PAPERS A Special Issue of JFP on Semantics, Applications, and Implementation of Program Generation http://cs-www.cs.yale.edu/~taha/saig/jfp.html Program generation has the prospect of being an integral part of a wide range of software development processes. Recent studies investigate different aspects of program generation systems, including their semantics, their applications, and their implementation. Existing theories and systems address both high-level (source) language and low-level (machine) language generation. A number of programming languages now support program generation and manipulation. These languages can have different goals, use different different implementation techniques, and target different applications. In this context, a PLI workshop dedicated to this theme (SAIG'00) was held this year. Following on from this workshop, a special issue of the Journal of Functional Programming will be devoted to the same theme. Full-length, archival-quality submissions are solicited on topics including both theoretical and practical models and tools for building program generation systems, Examples include: * Semantics, type systems, and implementations for multi-stage languages. * Run-time specialization systems: e.g. compilers, operating systems. * High-level program generation (applications, foundations, environments). * Symbolic computation, linking and explicit substitution, in-lining and macros. Reports on applications of these techniques to real-world problems are especially encouraged, as are submissions that relate ideas and concepts from several of these topics, or bridge the gap between theory and practice. Contributors to SAIG'00 are encouraged to submit, but submission is open to everyone. Papers will be reviewed as regular JFP submissions, and acceptance in the special issue will be based on relevance to the theme. The special issue also welcomes high-quality survey and position papers that would benefit a wide audience. Accepted papers exceeding the space restrictions will be published as regular JFP papers. Submissions should be sent to the guest editor (address below), with a copy to Nasreen Ahmad (nasreen(a)dcs.gla.ac.uk) Submitted articles should be sent in postscript format, preferably gzipped and uuencoded. In addition, please send, as plain text, title, abstract, and contact information. The submission deadline is February 1st, 2001. For other submission details, please consult an issue of the Journal of Functional Programming or see the Journal's web page at http://www.dcs.gla.ac.uk/jfp/. Guest Editor Editor in Chief Walid Taha Department of Computer Science Philip Wadler Yale University Avaya Labs P.O. Box 208285 700 Mountain Ave, Room 2T-402, New Haven, CT 06520-8285, Murray Hill, NJ 07974-0636, USA. USA. Email: taha(a)cs.yale.edu Email: wadler(a)avaya.com Phone: +1 203 432 6496 Phone: +1 908 582 4004 Fax : +1 203 432 0593 Fax: +1 908 582 5857

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Re: library Directory.hs
by Sigbjorn Finne 27 Jun '01

27 Jun '01

Nicole Gabler Nicole.Gabler(a)web.de writes: > > thank you for all your answers. I solved the problem without > using Directory.hs, but now I have a new problem and now > I need Directory.hs. I only have the name of a directory and I > have to search for any files in this directory! Unfortunately, the > business concern, where I'm doing an industrial practical, don't > use Unix but Windows NT. So, what can I do?? Hi, I'd suggest either waiting for the next release of Hugs98, or grab a copy of the Hugs98 sources from the CVS repository (http://cvs.haskell.org/ & compile it up. It has a complete set of Haskell98 modules, including Directory. If neither of these options are practical, let me know & I'll send you a copy of the files you need. hth --sigbjorn

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Re: hbc
by Stephen Bailey 27 Jun '01

27 Jun '01

> Why hbc did not succeeded? I heard rumors that the author went off to some cushy industrial job, or is spending all his time writing NetBSD drivers, or something like that :^) Steph

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Re: library Directory.hs
by Nicole Gabler 27 Jun '01

27 Jun '01

Hello All, thank you for all your answers. I solved the problem without using Directory.hs, but now I have a new problem and now I need Directory.hs. I only have the name of a directory and I have to search for any files in this directory! Unfortunately, the business concern, where I'm doing an industrial practical, don't use Unix but Windows NT. So, what can I do?? Thanks, Nicole

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adventure game
by stanley goof 25 Jun '01

25 Jun '01

Hi everybody, I am planning to write a text-adventure game in haskell. This is the type of game in which you can execute many commands like 'take'(to take an object), 'goto' to move from a room to another room, 'look'(to see the objects in a room), 'open'(to open a drawer), ... I'm currently studying haskell, so i'm a beginner. If you know any hints or any sources which can help writing this game, write me. Thank you very much ___________________________________________________________ Do You Yahoo!? -- Pour faire vos courses sur le Net, Yahoo! Shopping : http://fr.shopping.yahoo.com

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(no subject)
by Manjula Iyer 25 Jun '01

25 Jun '01

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new version of parser combinators
by S. Doaitse Swierstra 23 Jun '01

23 Jun '01

We have been working hard on new versions of the Parser Combinators and AG system, with the following improvements: even better error repairs much faster and simpler basic parsing machine permutation (of different types) and list combinators extensive reporting about repairs made and what was expected the possibility to manipulate your own state during parsing and result construction, using classed based (like monads) interfaces As an example of the permutation combinators we parse a permutation of three elements: 1) a list of 'a's 2) a 'b' 3) an optional 'c' which is described by: permtest :: Parser Char (String, Char, Char) permtest = permute $ (,,) ~$~ pList (pSym 'a') ~*~ pSym 'b' ~*~ pOptSym 'c' pOptSym :: Char -> Parser Char Char pOptSym x = pSym x <|> pSucceed '_' which we try on several inputs resulting in: t permtest "acb" Result: ("a",'b','c') t permtest "cdaa" Errors: Symbol 'd' before 'a' was deleted, because 'b' or ('a')* was expected. Symbol 'b' was inserted at end of file, because 'a' or 'b' was expected. Result: ("aa",'b','c') t permtest "abd" Errors: Symbol 'd' at end of file was deleted, because 'c' or eof was expected. Result: ("a",'b','_') t permtest "" Errors: Symbol 'b' was inserted at end of file, because 'c' or 'b' or ('a')* was expected. Result: ("",'b','_') The manual is still of an earlier version and will be adapted soon. As an example of the combinators we provide a parser for bibtex files, that returns the repairs made to the erroneous entries (as far as we understand the bibtex format). I hope this is useful to you, Doaitse Swierstra

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User Generated Database of Internet Social Communities
by Jeff Cohn 23 Jun '01

23 Jun '01

We have launched a new research database and would appreciate the contribution of you and your students. http://ecultures.homestead.com/ecultures.html A User Generated Database of Internet Social Communities eCultures is a research tool established to address growing need to discover the Internet's vast network of virtual communities around the world. Unlike today's commercialized and non-collaborative search engines, eCultures has taken a new approach to collaborative research by allowing users to immediately share and search under one common database. All submissions are subject to a review. eCultures is a web property of eStrategy Partners, LLC Comments are appreciated! Regards, Jeff Cohn President & Founder eStrategy Partners, LLC Office: 310-546-7539 jcohn(a)estrategypartners.com www.estrategypartners.com "Solutions for eBusiness"

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